VT-x is disabled in the BIOS for both all CPU modes (VERR_VMX_MSR_ALL_VMX_DISABLED)

It is a RAM related issue. The documentation is self explanatory:

You are trying to allocate >3GB of RAM to the VM. This requires: (a) a 64 bit host system; and (b) true hardware pass-through ie VT-x.

Fast solution

Allocate less than 3GB for the virtual machine.

Complete solution

1. Make sure your system is 64 bit.
2. Enable virtualisation in your host machine. You can find how to do it here or there are many other resources available on Google.

Turning PAE/NX on/off didn't work for me. I just needed to turn on virtualization on my computer. I was working on a HP Compaq 8200 and followed the steps below to turn on virtualization. If you are working on a different computer, you probably just need to look up how to turn on virtualization on your pc. The steps below for HP Compaq 8200 (or similar) is copied verbatim from the comment posted by the user qqdmax5 on Hp discussion board here.

To run Oracle VM Virtual Box / VMware machines on 64-bit host there is a need to enable Virtualization Technology (VTx) and Virtualization Technology Directed I/O (VTd).

Usually these setting are disabled on the level of BIOS.

To enable VTx and VTd you have to change corresponding settings in the BIOS.

Here is an example how to do it for HP Compaq 8200 or similar PC:

1. Start the machine.
2. Press F10 to enter BIOS.
3. Security-> System Security
4. Enable Virtualization Technology (VTx) and Virtualization Technology Directed I/O (VTd).
5. Save and restart the machine.

There is also some discussion on this on askubuntu.

In Virtual Box "Settings" > System Settings > Processor > Enable the PAE/NX option. It resolved my issue.

I had this issue when tried to run a 32-bit OS with more than 3584 MB of RAM allocated for it. Setting the guest OS RAM to 3584 MB and less helped.

But i ended just enabling the flag in BIOS nevertheless.

Follow the steps below in Oracle VM VirtualBox Manager:

1. Select the Virtual device and choose Settings
2. Navigate to System and click the Processor tab
3. Tick the check-box, Enable PAE/NX
4. Click OK and you are done

To verify, start the Virtual device from Oracle VM VirtualBox. If all has gone well, the device boots up.

Close this device and open it from Genymotion.